Conventional electric household continuous flow heaters include one or multiple heating blocks, each including at least one heating channel that has generally a meander-shaped design, through which in each case liquid (in particular water) may be passed through, and in which a heating coil is situated.
This type of heating block may include, in at least one section, two assembled heating block half-shells. Each of the heating block half-shells may form a partial wall for the heating channel. When the two heating block half-shells are assembled, the two partial walls together form a tube that encloses at least a portion of the heating channel.
The heating coil is formed from a heating wire that is generally helically wound around a coil center. The heating coil represents an electrical resistor that heats up when electrical current passes through, and releases heat to the water flowing around it.
To avoid local overheating (resulting in the formation of so-called “hot spots”) and also to prevent adhesion of air bubbles and the mechanical oscillation of the heating coil (with accompanying noise emissions), the heating coil must be mounted in the heating channel in a suitable position.
For this purpose, in conventional heating blocks, a heating channel is formed in such a way that narrow guide ribs center the heating coil in the heating channel. Between straight sections, the heating channel includes turning sections in which the channel routing is deflected by 180°. The guide ribs each extend across the straight sections of the heating channel, and grip the helically wound heating coil on its outer side.
The guide ribs create spaces between the heating coil and an inner wall of the heating block (which forms a wall of the heating channel) and position the heating coil in the center of the heating channel. Water that is conducted through the heating channel thus flows to a small extent through the (outer) spaces, and to a different, greater extent through an open space in the middle of the heating coil.
An increased flow resistance occurs in the spaces, and in particular the guide ribs generate disadvantageous turbulences, and the flow velocity in the spaces is reduced. Uniform flow of water, to be heated, around the heating coil is thus prevented.
In an alternative approach that is described in German Patent Application No. DE 10 2012 013 348 A1, the heating channel includes an undulated section with a heating coil fixed to its ends. Due to the undulation of the section, the heating coil rests against the heating channel wall at various locations, and is thereby positioned.
However, in such heating channels an increased flow resistance is generated due to the undulation. In addition, the heating blocks with undulated sections are costly to manufacture.